It is desired that most audio-related systems (e.g. a TV, a computer, an audio recognition device, a video camera, or the like) selectively receive desired signals. However, in environments where noise or echo is present, a variety of signals other than the desired signal is produced and is received together with the desired signal by a microphone. A variety of technologies, such as an array of directional microphones, noise reduction, acoustic echo cancel or blind source separation, is being studied in order to remove noise or echo.
An audio-related system receives a mixed signal in which a desired signal is mixed with an undesired signal, such as noise or an echo, through a microphone or microphone array. Therefore, the signal level of the undesired signal contained in the mixed signal causes a problem in the audio-related system in performing a desired operation or an inconvenience to a user.
For instance, when the audio-related system is a system which recognizes an audio command, a problem of lowered audio recognition rate can be created. If the audio-related system is intended to mainly record sound received in a particular direction (e.g. a direction in which pictures are recorded) as in a video camera or a camcorder, undesired sound received in other directions (e.g. a direction from behind) can be sound that a user does not want to record or receive.
Therefore, separating desired sound from undesired sound has a great influence on the performance of audio-related systems and the utility and convenience of the user.
A variety of technologies for separating desired sound from undesired sound is well known. Undesired sound can be sound that is known or unknown to the system. For instance, a published Korean patent application filed by the applicant (or the representative of applicants) (Korean Patent Application No. 10-2009-0111323, “SIGNAL SEPARATION METHOD, AND COMMUNICATION SYSTEM AND AUDIO RECOGNITION SYSTEM USING THE SIGNAL SEPARATION METHOD,” hereinafter referred to as “previously filed application”) disclosed a technical concept in which the above-described audio-related system effectively separates a known undesired sound from a mixed signal in real time. The disclosure and descriptions of the previously filed application can be incorporated herein by reference.
In addition, irrespective whether or not the undesired sound is known to the audio-related system, a variety of methods for separating the desired sound from the undesired sound contained in the mixed signal (e.g. least mean square (LMS), blind source separation (BSS) or independent component analysis) is also present.
However, most of these conventional methods require a hardware structure to be accurately designed from the point of time when the audio-related system is designed and produced or separate hardware or software resources for using the known undesired sound in the signal separation process. Otherwise, there is another problem in that calculation is too complicated and thus not appropriate for separating the desired signal from the undesired signal in real time.
Therefore, there is required a technical concept with which a desired signal can be separated from a mixed signal simply and efficiently without a change in the hardware structure of the audio-related system or consumption of expensive hardware and/or software resources for signal separation.